Electronic tube and circuit therefor



Oct. 18, 1955 E. E. SANFORD ELECTRONIC 'I'UBEi AND CIRCUIT THEREFOR Filed Oct. 8, 1951 IN V EN TOR. EM/L E. SANFORD BY A A TTORNE YS Unite 2,721,253. Patented Get. 18, 1955 ELECTRONIC TUBE AND CIRCUIT ri nnnron Emil E. Sanford, Clifton, N. 5., assignor to Allen B. Du Mont Laboratories, Inc., (Ilifton, N. 3., a corporation of Delaware Application October 8, 1951, Serial No. 250,233 Claims. (Cl. 250-27) This invention relates to electronic tubes and circuits therefor, and more particularly to such tubes and circuits which utilize pulse signals.

An object of the invention is to provide an electronic tube and associated electrical circuit in which desired sig nals are produced and undesired signals are suppressed or damped out.

Another object is to provide an electronic tube having therein an element which functions as an anode or currentcollector and also as a cathode or current-emitter.

A further object is to provide an electronic tube in which a cathode is heated to electron-emissive temperature by means of electron bombardment.

Other objects will be apparent.

In the drawing, Figure 1 shows a side elevational view of an electronic tube containing a structure in accordance with the invention;

Fig. 2 is a sectional view of Fig. 1 taken on the line 2-2, showing the internal disposition of elements/ Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2, showing internal arrangement of elements.

Fig. 4 is a schematic diagram of the novel tube connected in a preferred electrical circuit.

Fig. 5 is an alternative electrical circuit utilizing the novel electronic tube.

Referring to Figures 1, 2, and 3, the electronic tube comprises an envelope 11 preferably of glass, having attached thereto a base 12 from which connector pins 13 extend. Within the envelope 11 is a structure 16 which comprises a cathode 17 comprising electron-emissive material, such as carbonates of barium, strontium, and calcium, which emissive surface is capable of emitting electrons when thermally heated to proper temperature. Surrounding the cathode 17 is a control grid 18 comprising a mesh-like structure constructed and supported in a wellknown manner. A screen grid 19 is positioned to surround the control grid 18, and is constructed and supported in a manner well-known in the art. In Fig. 3, these grids are shown to be formed from wires wound in a helical manner. Baflies 21 are positioned to partially surround the screen grid 19. An anode 22, shown as comprising two sections, is positioned to be exposed to electrons emitted from the cathode 17.

Electron-emissive material 23 is attached to parts of the surface of the anode 22, which parts are shielded from the cathode 17 by the anode 22. A collector element 24 is positioned around the anode 22 and emissive material 23, and is shown to comprise two separate portions coinciding with the two separate portions of the anode 22.

Referring to Figure 4, a source 31 of input signals is connected to the cathode 17 and to the control grid 13 through a condenser 32. The source 31 of signals may be, for example, deflecting signals for electron-beam deflection in a television picture tube. A resistance 33 is connected between the control grid 18 and cathode 17. A first source 34 of voltage is connected between the cathode 17 and the screen grid 19. A second source 35 of voltage is connected between the screen grid 19 and the anode 22 through a load impedance 36 which may be, for example, a deflection coil or yoke for deflecting an electron beam in a television picture tube. The collector element 24 is connected to the screen grid 19 Referring to Figure 5, the source 31 of input signals is connected between the control grid 18 and cathode 1 7 through a bias resistance 41. The first source 3% of voltage is connected between an end of the resistance 41 and the screen grid 19. The second source 35 of voltage is connected between the screen grid 19 and anode 22 through a primary winding 42 of a load transformer 43. A secondary winding 44 of the transformer 43 is connected to a load circuit 46 which may comprise a deflection yoke or coil for a television picture tube. One end of the secondary 44 is also connected to the junction of the cathode resistance 41 and the first source 34 of voltage. The remaining end of the secondary 44 is connected to the collector element 24.

The novel tube functions as follows:

The cathode 17, the control grid 18, the screen grid 19, the bafiies 21, and the anode 22, operate in a wellknown manner similar to that of tubes known in the art as beam power tubes. Both portions of the anode 22 are constructed of suitable material and have such a size as to be heated, during normal operation, by the cathodeemitted electrons striking the inner surface thereof. A preferred material for the anode 22 is tantalum. It is desired that the anode 22 be heated, by normal electron bombardment, to a sufiicient temperature so that the electron-emissive material 23 will emit electrons. Such a heat is generally characterized by a dull red color. The amount of such heating can be controlled during manufacture of the tube by altering the thickness, width, or height of the portions of the anode 22.

Under certain conditions it may be desirable to extend the anode portions completely around the baffles 21 so that the anode 22 will comprise a cylinder. The heating of the anode may also be controlled by adjustment of certain circuit components, such as the cathode-bias resistor 41 or by the magnitude of signals supplied by the signal source 31, or by adjusting the magnitudes of voltages supplied by the voltage sources 34 and 35, and also by the design of the load elements 36, 43 and 46. The electrons emitted by the anode-emitting portions 23, will flow to the collector elements 24 when these elements are at a positive polarity with respect to that of the anode 22. The circuit of Fig. 4 operates as follows: The cathode 17, control grid 18, screen grid 19, and anode 22, amplify the signal supplied by the signal source 31 in a well-known manner. The amplified signal is supplied to the load impedance 36. In television sweep circuits, the signal generally comprises pulses or abrupt changes in amplitude, from which undesired pulses are generated due to inductive reaction in the load element 36. These undesired pulses are of such a polarity as to place, temporarily, the collector element 24 at a positive potential with respect to that of the anode 22, whereby current flows between these elements and thereby shortcircuits or damps out these undesirable pulses. If these undesirable pulses were not damped out, they would produce undesirable results such as, for example, a phenomenon known as ringing which causes modulations of the electron beam in a television picture tube. The circuit of Figure 5 operates in a manner similar to that of Figure 4. The load circuit, however, comprises a transformer coupling between the tube and the load 46. The transformer 43 provides the proper output pulse voltage ratio. When the control grid 18 is driven positive by a signal from the signal source 31, the anode 22 receives electrons and the end of the primary 42 which is connected to the anode 22, tends to become relatively negative. At the same time, the end of the secondary 44 which is connected to the collector 24, tends to become relatively positive.

Following a relatively negative change in control grid 18 potential produced by the signal source 31, the current between the cathode 17 and anode 22 decreases. Because of a well-known inherent characteristic of inductances, known as self-induction, the anode end of the primary 42 continues to become temporarily more negative and the collector end of the secondary 44 continues to become temporarily more positive. When these temporary voltages reach a point at which the anode 22 is relatively negative with respect to the collector 24, electron emission occurs between the anode emitter 23 and the collector 24, and thus short-circuits or damps out the undesired pulses or oscillations. The connections to the secondary 44 may be reversed, when required, to obtain proper damping polarity. The impedances of the voltage sources 34, 35 are sufficiently low so that the effective damping path is through the primary 42, the secondary 44, and between the elements 23 and 24.

The novel electronic tube is, in a sense, a dual-purpose tube wherein one element, namely the anode 22, functions both as an anode or electron-collector and as a cathode or electron-emitter. Power which normally might be wasted at the anode is effectively utilized as a heating source for the electron-emissive material 23 on the anode 22 which functions as the cathode for the collector element 24. Thus, not only is a separate tube eliminated but also the necessity for supplying filament or heating power thereto is also eliminated by the novel device herein disclosed.

Although a preferred construction of the novel device and circuits therefor have been described, modifications thereof will be apparent to those skilled in the art. The true scope of the invention is defined in the claims.

What is claimed is:

1. An electronic circuit comprising a tube having a first cathode, an anode positioned to receive electrons from said cathode, a control grid positioned to control said electrons, a second cathode connected to said anode, and a collector positioned to receive electrons from said second cathode; a source of signals connected between said first cathode and said control grid; a load circuit and a voltage source connected in series between said first cathode and said anode; and an electrical connection between said collector and said voltage source.

2. An electronic circuit comprising a tube having a first cathode, an anode positioned to receive electrons from said cathode, a control grid positioned to control said electrons, a second cathode connected to said anode, and a collector positioned to receive electrons from said second cathode; a source of signals connected between said first cathode and said control grid; a transformer having a primary and a secondary; an electrical connection between one end of said primary and said anode; a voltage source connected between said cathode and the remaining end of said primary; an electrical connection between on end of said secondary and said collector; an electrical connection between the remaining end of said secondary and said first cathode; and a load circuit connected to the ends of said secondary.

3. An electric circuit comprising a thermionic tube and an inductive load circuit, said tube having an output electrode adapted to be heated by operation thereof, an electron emissive element positioned to be heated by said output electrode to induce emission of electrons from said element, and a collector electrode positioned to receive said electrons from said emissive element, said inductive load circuit being connected to receive signals from said output electrode and electrically connected in a circuit between said element and said collector, to damp out undesired self-induced signals.

4. An electronic circuit comprising a thermionic tube, a source of signals and a load circuit, said tube having a first cathode, an anode positioned to receive electrons therefrom, a control grid positioned to control said electrons, a second cathode positioned to be heated by said anode and a collector electrode positioned to receive electrons from said second cathode, said source of signals being connected between said first cathode and said control grid and said load circuit being connected between said first cathode and said anode and also between said second cathode and said collector.

5. An electronic circuit comprising a tube having a cathode, an output electrode and a collector element, the obverse side of said output electrode positioned to receive electrons emanating from said cathode and adapted to be heated by operation thereof, a control grid positioned to control said electrons, a source of signals connected between said cathode and said control grid, the reverse side of said output electrode having electron emissive material thereon and heated by said output electrode to induce emission of electrons from said emissive material, said collector element positioned to receive electrons from said emissive material, a transformer having a primary and a secondary, a direct connection between one end of said primary and said output electrode, a source of voltage connected between said cathode and the remaining end of said primary, a direct connection between one end of said secondary and said collector element, a direct connection between the remaining end of said secondary and said cathode and a load circuit connected to the ends of said secondary.

References Cited in the file of this patent UNITED STATES PATENTS Re. 20,221 Macksoud Dec. 29, 1936 1,419,547 Ehret June 13, 1922 1,727,373 Macksoud Sept. 10, 1929 1,850,957 Foster Mar. 22, 1932 1,864,591 Foster June 28, 1932 1,999,327 Holden Apr. 30, 1935 2,107,520 Schade Feb. 8, 1938 2,228,980 Steimel et al. Jan. 14, 1941 2,308,908 Bahring Jan. 19, 1943 2,452,044 Fox Oct. 26, 1948 2,552,047 Kurshan May 8, 1951 2,615,138 Grimm Oct. 21, 1952 

